COVID-19

Viral tests are swab or saliva tests.

• They can show if you have a current infection.
• There are two main types of viral tests: antigen tests and nucleic acid amplification tests (NAATs). Most self-tests are antigen tests.
  • Antigen tests are rapid tests that give results in 10-30 minutes.
    • Antigen tests are less accurate than NAATs. This means that they are more likely to give false results, especially false negatives. Since antigen tests are less accurate, it is recommended that negative tests be repeated at least 48 hours later. See FDA instructions on repeat testing.
    • If you are doing a self-test, it is very important to follow the manufacturer’s step-by-step instructions exactly, including any instructions for repeat testing.
    • Sometimes a follow-up NAAT may be recommended to confirm an antigen test result.
    • Antigen tests are the best test for people who have tested positive in the last 90 days.
  
  
  • NAATs, such as PCR and LAMP tests, are usually performed in a laboratory.
    • PCR tests are the most accurate type of NAAT test for COVID-19. NAAT tests are less likely to give false results than antigen tests. They are sometimes used to confirm the results of rapid tests.
    • NAATs detect genetic material from the COVID-19 virus. If you get a COVID infection, this genetic material can stay in your body for up to 90 days. For this reason, NAATs are not recommended for people who have had COVID until 90 days have passed since their first positive test.
    
    
• See Self-tests-free kits and how to test to learn more, including how to tell if your test is good to use after it is past its expiration date.
• See Understanding Your Viral Test Result and What to do Next for more information.

Antibody tests (also known as serology tests) are blood tests.

• They might tell you if you had an infection in the past, but they cannot tell you when.
• They should not be used to test for a current infection or to tell if you are protected from getting COVID-19 in the future.

	VIRAL TESTS (swab or saliva tests) Looks for current infection		ANTIBODY TEST (blood tests) Looks for past infection
	NUCLEIC ACID AMPLIFICATION TEST (NAAT) (molecular tests e.g., PCR and LAMP*)	ANTIGEN TEST (most self-tests are antigen tests)	ANTIBODY TEST (serologic test or serology)
How the test works	Detects genetic material (RNA) within the COVID-19 virus	Detects proteins (or antigens) on the surface of the COVID-19 virus	Detects antibodies made by the immune system
How the test is done	Saliva, or swab from nose or throat	Swab from nose or throat	Blood from arm or finger stick
How long it takes to get results	Same day and up to 3 days. Some are rapid (around 20 minutes)	Most are rapid, around 10-30 minutes	Same day and up to 3 days
Over the counter self-tests	A few companies make them	Many companies make them	Not available

*Includes PCR (e.g., Reverse-Transcriptase Polymerase Chain Reaction - RT-PCR) and Loop-Mediated Isothermal Amplification (LAMP)

• If you have COVID-19 symptoms.
• If you have been a "close contact" to someone with COVID-19. See ph.lacounty.gov/covidcontacts.
• If you have COVID-19. Testing negative is strongly recommended before ending isolation between Day 6-10. Another reason to test is if you want to stop wearing a mask between Day 6 and Day 10. It is best to use an antigen test for this. See ph.lacounty.gov/covidisolation.
• Before and after travel. See CDC Travel for current recommendations.
• Before and/or after attending a gathering or event, especially if you will be around people who are at high risk for severe illness.
• If recommended by a healthcare professional or Public Health.

Note: There may be other settings that have their own testing requirements.

If you had COVID-19 within the last 90 days, you should test if you have symptoms of COVID-19. You should also test if you are a close contact to someone with COVID-19 and it has been 31-90 days since your first positive test. Otherwise, testing is not usually recommended. If you do test within 90 days of your first positive COVID-19 test, use an antigen test rather than a NAAT.

Talk with your doctor to make sure you understand what your test result means and any next steps. If you took a self-test, read the manufacturer’s instructions on how to interpret the test results. If you need advice about what to do next, you can also call the DPH COVID-19 information line at 1-833-540-0473.

COVID-19 antibody tests (also known as serology tests) are blood tests that are used to look for antibodies to SARS-COV-2 (the virus that causes COVID-19). If we get COVID-19 or a COVID-19 vaccine our body’s immune system responds. It makes antibodies and prepares our immune cells to be ready to fight the virus in the future.

COVID-19 antibody tests do not look for the actual SARS-CoV-2 virus itself. They can be used to help figure out if someone was infected with COVID-19 in the past. It takes about one to three weeks after becoming infected for the body to make enough antibodies to be found by a test. Some people may take even longer, and some people who were infected with COVID-19 may never develop antibodies. NONE of the currently authorized tests are recommended to see if people have been successfully vaccinated against COVID-19.

Antibody tests are not 100% accurate, so false results may occur. Talk to your doctor before being tested for antibodies. Your doctor can help you decide if you should be tested and, if you are tested, tell you what your results mean. To learn more about antibody tests, visit the CDC webpage.

• CDC COVID-19 Testing: webpage with links to pages on types of tests and FAQs
• FDA Coronavirus Basics: webpage explains the different types of tests, and how they are performed and approved.